The objective is to determine the extent to which the multi-year implementation of a realistic multi-component school-based smoking prevention intervention can reduce smoking prevalence in the junior high years and maintain the reduced prevalence throughout and beyond high school. The intervention to be evaluated consists of the entire intervention process, which includes coordination with state education officials, teacher training, program monitoring, teacher feedback, curriculum modification, and the curriculum itself. The study population will be approximately 8,000 students in 40 geographically and demographically diverse high school feeder systems in the State of Washington. With the feeder system as the unit of intervention, two consecutive cohorts in each of 20 experimental and 20 control feeder systems will be followed for endpoint determination through and beyond high school. Smoking behavior endpoints will be obtained in grades 5, 7, 9, and 12, and two years after high school. The methodology of randomized controlled clinical trials will be adapted to this prevention study, with special attention given to address the dual problems of contamination and follow-up inherent in prevention follow-up studies. Tracking methods, including follow-up data files, will be established at the beginning of the study, and updated periodically, to permit tracking and follow-up of cohort individuals who leave the feeder system. The intervention will be sustained throughout the entire period of adolescent smoking onset, and will include early preparatory (to risk of smoking onset) components starting in the 3rd grade. The intervention curriculum will be adapted from existing curriculum: (1) the Project CHOICE curriculum (grades 3-5), developed jointly by the Fred Hutchinson Cancer Research Center and the State of Washington Office of the Superitendent of Public Instruction; (2) the (Waterloo) Keep It Clean curriculum (grades 6-9); and (3) the (Minnesota) Keep It Clean Ii curriculum (grade 10). The project has been developed collaboratively by the Fred Hutchinson Cancer Research Center, the University of Washington School of Public Health and Community Medicine, and the State of Washington Office of Superintendent of Public Instruction.